Prevalence and risk factors of seizure in children with acute bacterial meningitis: updating previous evidence using an epidemiological design

Objective The current study aimed to investigate the prevalence and risk factors of seizure in acute bacterial meningitis. Materials & Methods In the present study, a total of 180 children (age range, 2 months to 14 years) with acute bacterial meningitis, were separated into two groups based on the diagnosis of seizure. The study was conducted in Mashhad (Iran) from 2002 to 2016. Results Seizure occurred in 37.4% of children with bacterial meningitis. Streptococcus pneumonia (S. pneumonia) was the most common organism. Most of the children with seizures (53.7%) had more than one episode. Also, 35% of patients had neurologic complications. Complications were more related to the seizure occurrence, the number of episodes, prolonged seizure, and being younger than 12 months. Age categories of less than 1 year and 1-5 year were associated with increased risk of seizure (odds ratio: 4.33 and 6.54, respectively). The more episode of seizure was associated with more complications (odds ratio: 6.33). Conclusion The prevalence of seizures in acute bacterial meningitis was 37.4%. Besides, the seizure was associated with more complications. Hence, timely diagnosis and treatment of bacterial meningitis are necessary for preventing future consequences.


Introduction
Acute bacterial meningitis (ABM) is a lifethreatening infection with high morbidity and mortality in neonates and young children (1,2). Every year it claims more than 171000 life worldwide (3). The mortality rate of bacterial meningitis ranges from 2 to 30% (3). Also, 10-20% of survived cases suffer from epilepsy and mental retardation (1). The mortality rate of ABM depends on age, pathogen, and geographic location (3). Furthermore, its epidemiology has changed considerably in the countries that adopted the conjugate vaccines against Haemophilus influenza type b, Neisseria meningitides, and S. pneumoniae (4). The ABM carries a higher burden in developing countries (4). Seizure is a common and unwelcome outcome of bacterial meningitis. The incidence rate of seizure in patients who suffer from ABM varies from 25 to 50% (5-7). Our literature review revealed that no recent study has been conducted on this issue in Iran, as a developing country. Hence, following a retrospective design (2002 to 2016) the current study aimed to evaluate the prevalence and risk factors of seizure in infants and children with acute bacterial meningitis in Iran. Bacterial meningitis can be confirmed by isolation of a bacterial pathogen from a normally sterile clinical specimen such as CSF or identification of a bacterial antigen in normally sterile fluids or gram stain results.

Sample size
Following the enumeration method, the sample size was estimated at 180 subjects.

Analysis
Data were analyzed using SPSS version 16 Table 1.

Organisms
According to smear and CSF culture, S. pneumoniae was found in 16 (23.9%) patients with seizure and 25 (22.7%) without seizure. H. influenza type b was found in 4 (6%) and 12 (10.9%) patients with and without seizure, respectively. Forty-four (65.7%) and 67 patients (60.9%) with and without seizure had negative results, respectively. There was no significant difference between the study groups concerning the responsible organism (p=0.54).
Also, the type of the organism was not different in patients with and without seizure. The results are presented in Table 2. Seizure characteristics are presented in Table3.

Seizure characteristics
There was a significant difference concerning the seizure occurrence, the number of seizure episodes, prolonged seizure, and being younger than 1 year old (p=0.002, 0.002, 0.007, and 0.0001, respectively). Complications were not significant according to the type of seizure, time of first seizure episode, gender, and mortality (p>0.05).  Table 4.

Risk factors
According to the results of the logistic regression, age less than 1 year and the age group of 1 to 5 years old had a significant association with seizure occurrence ( (5,8,9,11). Also, according to the findings, the rate of mortality was 3.3%, which is in line with several studies that reported a prevalence of 3.8 to 12% (12)(13)(14)(15).
In our study, being younger than one-year-old and influenza infection in children with meningitis was 11.4% before vaccination, which decreased to 3.2% after vaccination, which in turn indicates the critical role of vaccination in the prevention or decrement of bacterial meningitis.

In Conclusion
To conclude, the prevalence of seizure in patients with acute bacterial meningitis was 37.4%. Because of the significant association between seizure and complication, it is necessary to pay more attention to the exact and on-time diagnosis of acute bacterial meningitis, as it can decrease both hospitalization and cost of treatment and is associated with increased quality of life.
According to the findings, we suggest routine administration of S. pneumoniae vaccine for children aged 2, 4, and 6 months as well as those aged 12-18 months in Iran.